# Effectively replace a key in a dictionary
**URL:** https://discourse.julialang.org/t/effectively-replace-a-key-in-a-dictionary/92018
**Category:** General Usage
**Created:** [December 22, 2022, 7:05pm UTC](https://discourse.julialang.org/t/effectively-replace-a-key-in-a-dictionary/92018 "2022-12-22T19:05:37Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@andrey2185](https://discourse.julialang.org/u/andrey2185)
#### Post date: [December 22, 2022, 7:05pm UTC](https://discourse.julialang.org/t/effectively-replace-a-key-in-a-dictionary/92018/1 "2022-12-22T19:05:37Z")
Hello, please tell me a way to effectively replace a key in a dictionary, or a package that implements a data structure that allows you to do this, due to a fixed number of key-value pairs
i have too many allocations, it is bad
```julia
using BenchmarkTools
n = 10^6;
d = Dict([i => i for i = 1 : n]...);
keys = [rand(1:n) for i in 1:2*n];
replace_keys(d, n) = for k in keys
if !haskey(d, k)
pop!(d)
d[k] = k
end
end;
@btime replace_keys(d, keys); # -> 320.215 ms (5998457 allocations: 122.05 MiB) !!!
```
---
### Author:  [@andrey2185](https://discourse.julialang.org/u/andrey2185)
#### Post date: [December 22, 2022, 7:16pm UTC](https://discourse.julialang.org/t/effectively-replace-a-key-in-a-dictionary/92018/2 "2022-12-22T19:16:54Z")
sorry, bug
---
### Author:  [@andrey2185](https://discourse.julialang.org/u/andrey2185)
#### Post date: [December 22, 2022, 7:20pm UTC](https://discourse.julialang.org/t/effectively-replace-a-key-in-a-dictionary/92018/3 "2022-12-22T19:20:51Z")
can i delete this topic?